Some naturally occurring resources, such as gas hydrates, dissociate or form, or are otherwise affected, when temperature and/or pressure conditions cross the equilibrium border. An understanding of the parameters for such behavior is important for efficient exploration and development of the resources, for example, gas hydrates and heavy oils as energy resources. In this, thermal measurements are one of the key components in characterizing subsurface structures, not only statically but also dynamically.
Conventional methods to estimate thermal properties, such as thermal conductivity, capacity and diffusivity, of subsurface formations include monitoring temperatures passively at several underground depth locations and interpreting the collected data with assumptions such as steady heat flow or relaxation from thermal disturbance by drilling and/or mud circulation, etc. In conventional systems, temperature changes caused by a production test or drilling/circulation operations are measured. Because the thermal properties are estimated based on several assumptions, the passive measurement methods described above leave large uncertainties in the estimated thermal properties of the subsurface structures.
On the other hand, active thermal property measurements may be undertaken in a laboratory and equipment is commercially available for these purposes. However, applications of the laboratory based active measurement methods to in situ subsurface formation measurements have many technical and logistical difficulties.